The present invention relates to an orthopedic system and, more particularly, to an improved orthopedic system wherein the part of the device that attaches to the bone is detachable from the parts of the system which provide the bone fixation, reduction, distraction, etc.
A variety of orthopedic devices, including bone fixation, reduction, and distraction devices, are known in the art. Fixation devices, or fixators, are used to stabilize bone segments and to facilitate the healing of bones at a bone repair site. As used herein xe2x80x9cbone repair sitexe2x80x9d refers to any bone region which is bounded on opposing sides by relatively healthy bone regions to which orthopedic devices can be secured, such as an osteotomy or a fracture. Reduction and distraction devices (commonly referred to as reducers and distractors), are used to gradually adjust the relative orientation and spacing of the bone parts on opposing sides of a bone repair site.
Fixators generally consist of transcutaneous pins or screws secured in the bone on either side of the bone repair site. An adjustable external fixation mechanism is attached to the pins, allowing the relative positions of the pins to be adjusted, thus aligning the bone regions across the bone repair site. When the desired alignment is achieved, the fixation mechanism is locked in place to maintain the alignment. After the bone repair site has healed, the fixator is removed from the patient.
Reducers and distractors typically have structure similar to fixators, except that they additionally include a mechanism which allows controlled incremental adjustment of the distance between parts of the device on opposing sides of the bone repair site. Typically, distractors are used to perform distraction osteogenesis. This procedure was perfected by the Russian orthopedic doctor, Gavriel Ilizarov. A typical procedure of this type involves at most an osteotomy completely separating the bone into two segments, or at least an incision of the cortical portion of the bone. Then, the bone segments on either side of the osteotomy (or the medullary or cancellous portion of the bone on either side of the incision) may be expanded. This gradual separation allows new bone to form in the osteotomy void. The distraction phase is followed by a consolidation phase, during which the distractor is held fixed, and the new bone growth gains strength. Following the consolidation phase, the distractor is removed from the patient.
The design of the early fixators and distractors, which used bone pins and screws to attach the device to the bone are known to have certain problems. For example, numerous pins are needed to attach a single device; at a minimum, two pins are required, but typically, many more are used. Each pin involves a transcutaneous incision, thus multiplying the risk of infection to the patient. Furthermore, a pin clamp or coupling is required to join the fixation/distraction mechanism to the pins, and the design and operation of these couplings are complicated by the difficulty in aligning the pins accurately when they are inserted into the bone. Finally, because the pins extend in a generally perpendicular direction from the insertion site, they cause the resultant overall device to stick out quite far from the patient""s body (i.e., the device has a high profile), and the device is unsightly. A high-profile device is more subject to bumps and snags than one which is completely located close to the patient""s body. Such seemingly aesthetic considerations are also important because a high-profile device may be rejected by prospective patients, especially children.
Accordingly, more recent devices have been designed not to use transcutaneous pins for attachment to the bone, but rather to use more low-profile bone anchors, such as plates with screw holes, as part of a low-profile overall device. This improved prior art is exemplified by U.S. Pat. No. 5,364,396 to Robinson et al. (xe2x80x9cthe Robinson patentxe2x80x9d), which discloses an implantable bone distraction device which includes low profile blocks for attachment to osteotomically separated bone sections. The entire device can be implanted subcutaneously, except for a transcutaneous actuator assembly which is linked to the implanted distraction assembly, and allows adjustment of the distraction distance from outside the patient""s body.
However, modem low-profile fixation/distraction systems such as that disclosed in the Robinson patent suffer from the drawback that their use necessitates two substantial, invasive, surgical procedures: one to implant the device, and another to remove it after the fixation/distraction procedure is complete. Unnecessary surgical procedures are of course undesirable, based on both considerations of health care costs and the medical risks associated with surgery.
Accordingly, there is a need in the art to provide a low-profile fixator/distractor that does not require a second surgical procedure to remove the device after the fixation/distraction procedure is complete. Indeed, there is a need in the orthopedic device art more generally, to provide a device that does not require a second surgical procedure to remove the device after the orthopedic procedure is complete.
The present invention addresses the need in the art by providing an orthopedic device, such as a bone fixator, reducer, or distractor, with detachable bone anchors, such that after the completion of the orthopedic process, the orthopedic device can be remotely disengaged, from outside the patient, from the subcutaneous bone anchors, leaving only the subcutaneous bone anchors implanted in the patient.
The orthopedic system of the present invention includes at least two bone anchors. Each of these anchors has a bone-contacting surface and fastener-connecting portion. There is a fastener associated with each bone anchor; the fastener includes a device-connecting portion for connection to an orthopedic device (such as a distractor), and a anchor-connecting portion for establishing a releasable mechanical coupling with the fastener-connecting portion of the associated anchor. An orthopedic device, such as a distractor, is coupled to the device-connecting portions of each fastener in order to perform the desired procedure. After the orthopedic procedure involving the orthopedic device is complete, the mechanical couplings of the fasteners to the bone anchors can be released, allowing the fasteners and device to be easily removed from the patient without requiring the removal of the bone anchors.
The bone anchors may be in the form of bone plates, and may be made in full or in part from any appropriate bio-compatible material, such as a bio-absorbable (resorbable) material. When formed as bone plate, the anchors may have one or more screw holes adapted to receive a bone screw. The bone screws may also comprise a bio-absorbable material, in which case the material selected for the screws should be such that the screws will take at least as long to be absorbed by the patient""s body as the bone plates.
The releasable coupling of at least one of the bone anchors and fastener may comprise a detent mechanism. Preferably, the release of the detent mechanism is prevented when the orthopedic device is substantially fully coupled to the device-connecting portion of that fastener; this avoids undesired release of the system while it is in use. Release of the detent mechanism is permitted when the orthopedic device is at least partially uncoupled from the device-connecting portion of that fastener, such that the system can be disassembled when desired.
One of the fasteners may have an anchor-connecting portion comprising a shoe; in this embodiment, the bone anchor associated with that fastener will have a fastener-connecting portion comprising an engagement cavity. The shoe and cavity are sized and shaped to allow the shoe to be slidingly received by the cavity. The shoe and engagement cavity may have a corresponding substantially rectangular shape, in which case the releasable mechanical coupling of the fastener to the bone anchor is a slip lock. Alternatively, the shoe and the associated engagement cavity have a corresponding substantially tapered shape, in which case the releasable mechanical coupling of the fastener to the bone anchor is a frictional lock.
An orthopedic distraction system for distracting first and second osteotomically separated bone sections according to the present invention may comprise a distal bone plate, a distal fastener, a proximal bone plate, a proximal fastener, and a distraction device. The distal bone plate is designed to be subcutaneously implanted and attached to the first bone section, and is provided with screw holes adapted to receive bone screws, a bone-contacting surface, and a first engagement cavity having a substantially rectangular shape.
The distal fastener associated with the distal bone plate has a device-connecting portion and a shoe. The shoe is shaped and sized to correspond to the first engagement cavity. In this way, when the shoe is slidingly accepted by the first engagement cavity, a slip lock of the distal fastener to the distal bone plate is produced.
The proximal bone plate is also designed to be subcutaneously implanted, and is attached to the second bone section. The proximal bone plate has screw holes adapted to receive bone screws, a bone-contacting surface, and a second engagement cavity. A proximal fastener is provided, to be associated with the proximal bone plate; this proximal fastener has a device-connecting portion and a anchor-connecting portion. The releasable coupling of the proximal bone plate and proximal fastener comprises a detent mechanism. Release of the detent mechanism is prevented when a distraction device is fully coupled to the device-connecting portion of the proximal fastener, but release of the detent mechanism is permitted when the orthopedic device is at least partially uncoupled from the device-connecting portion of the proximal fastener. In use, the distraction device is coupled to the device-connecting portions of each fastener. According to the novel orthopedic system of the present invention, when desired, both fasteners can be released from their corresponding bone plates, allowing the fasteners and distraction device to be easily removed from the patient without requiring the removal of the bone plates.
Also disclosed is a method for treating bone sections on either side of a bone repair site. Bone anchors are attached to the bone on each side of the bone repair site, and fasteners are releasably coupled to each of the bone anchors, an orthopedic device is coupled to the fasteners, either before or after the fasteners are coupled to the anchors. The orthopedic procedure is performed using the orthopedic device, and the orthopedic device and fasteners may be removed. The removal of the orthopedic device and fasteners may be performed in any order. The method disclosed is compatible for use with all of the various embodiments of the novel distraction system described herein.
The method for treating a bone repair site according to the present invention generally comprises the following steps. An incision is made, for access to the bone repair site. One bone anchor is attached to the bone on each side of the bone repair site, and a fastener is releasably mechanically coupled to each of the bone anchors. An orthopedic device is mechanically coupled to the fasteners and is used in performing the desired orthopedic procedure. When the procedure is complete, the orthopedic device and fasteners are removed, in any order, from the patient. The incision is then closed, leaving the bone anchors attached to the bone.
More specifically, the method for treating a bone repair site on a patient according to the present invention comprises the following steps. An incision is made, for access to the bone repair site. A distal bone plate is subcutaneously attached to the bone; this distal bone plate has screw holes adapted to receive bone screws, a bone-contacting surface, and a first engagement cavity having a substantially rectangular shape. A distal fastener is releasably coupled to the distal bone plate, this distal fastener having a device-connecting portion and a first shoe, the shoe being shaped and sized to correspond to the first engagement cavity. The shoe is slidingly accepted by the first engagement cavity, producing a slip lock of the distal fastener to the distal bone plate. A proximal bone plate is subcutaneously attached to the bone, this proximal bone plate has a bone-contacting surface, a second engagement cavity, and screw holes adapted to receive bone screws. A proximal fastener is releasably mechanically coupled to the proximal bone plate; this proximal fastener has a device-connecting portion and a anchor-connecting portion. The releasable coupling of the proximal fastener to the proximal bone plate comprises a detent mechanism. An orthopedic device, such as a distractor, is coupled to the device-connecting portions of both fasteners, and is used to perform the desired orthopedic procedure. After the procedure is complete, the distal fastener is uncoupled from the distal bone plate and the proximal fastener is uncoupled from the proximal bone plate, allowing the fasteners and orthopedic device to be removed from the patient. Finally, the incision is closed, leaving the bone plates in the patient.